The invention relates to silicic acid esters to which fragrances are bound, preferably as 1-aza-3,7-dioxabicyclo[3,3,0]octane compounds or as monocyclic oxazolidines, and are suitable for adding fragrance to detergents and cleaning agents because they release the bound fragrances in hydrolysis.
Controlled release of ingredients in a wide variety of preparations, known as “controlled release,” is the subject matter of numerous publications and patent applications. In the field of detergents and cleaning agents, accelerated or delayed release of ingredients from the group of bleaching agents, bleach activators, surfactants, etc. is of special interest. Of excellent importance in this field is the release of fragrances because the product as well as the detergent and cleaning solution and the items treated with these agents are to be perfumed intensely and with a long-lasting effect. The situation is similar for cosmetic agents, but instead of the perfuming of a product there, rather it is the perfuming of skin or hair that is to be accomplished.
A fundamental problem in the use of fragrances here is that these are naturally volatile substances; otherwise no fragrance effect could be achieved. Therefore, with regard to the use of fragrances in detergents and cleaning agents, one is confronted with the same problem as in the use of cosmetic preparations, that although the fragrances are naturally volatile compounds, on the other hand one would like to achieve a long-lasting fragrance effect that is as uniform as possible. In addition, the fragrance impression of a perfume changes over time because the scents representing the fresh and light notes in the perfume evaporate more rapidly due to their high vapor pressure than the fragrances representing the heart notes and base notes.
In addition to the methods of applying fragrances to carrier materials and coating the scented carriers, or encapsulating fragrances or incorporating them into compounds (e.g. cyclodextrin-perfume complexes), there is also the possibility of chemically binding the fragrances to carrier media, whereby the chemical bond is broken and the fragrance is released slowly. Such a carrier-bound precursor of a fragrance is also known as a “pro-fragrance,” “pro-accord” or “fragrance delivery substance.” Examples of converting a fragrance into a carrier-bound precursor include the esterification of fragrance alcohols, and there is an extensive state of the art for this group of substances.
In the state of the art, there have been several proposals for binding fragrance alcohols to nonvolatile siloxanes from which they are released slowly by hydrolysis. Although there is also an extensive state of the art in siloxane esters of fragrance alcohols, problems often occur when using the aforementioned compounds in detergents and cleaning agents. Thus many of the known compounds cannot always be used in aqueous detergents and cleaning agents because they undergo hydrolysis even in the product and the delayed release therefore no longer occurs at a later point in time. This is even more so because the usual detergents and cleaning agents often have pH levels which further promote hydrolysis. Incorporation of the known siloxane esters into powdered detergents and cleaning agents is no longer so simple. Under conventional production conditions for compressed particle mixtures such as granulation or press agglomeration, the siloxane esters also tend to release the fragrance alcohol already during production, i.e. too early. There is therefore a need for providing fragrance precursors which will perfume the product, e.g. detergents and cleaning agents, as well as substrates treated with the products, in particular textiles, having the longest lasting effect possible.
Monomeric orthosilicic acid esters of fragrance alcohols are described in U.S. Pat. No. 3,215,719 (Dan River Mills), for example. This document also mentions delayed release of perfuming alcohols from mixed esters such as bis(eugenyloxy)-diethoxysilane or bis(cinnamoyloxy)diethoxysilane, whereby the central Si need not necessarily be bound only to oxygen. Oligomeric siloxane esters are not described in that publication.
Powdered or granular detergents and cleaning agent compositions containing silicon compounds “imparting a pleasant odor” are described in DE 28 44 789 (Dow Corning). The monomeric, oligomeric and polymeric silicon compounds disclosed therein do not necessarily have a central Si atom surrounded by four oxygen atoms. Oligomeric Si compounds with more than one fragrance alcohol ester group are also not described in this publication. US 20030207786 and US 20040067870 also describe pro-fragrances having an oxazolidine structure.
U.S. Pat. No. 6,861,402 describes pro-fragrances containing a fragrance aldehyde or a fragrance ketone in the form of an oxazolidine. For example, N-benzene-ethanolamine is reacted with a fragrance to yield a monocyclic oxazolidine.